 This finding out what the psoas muscle is. Psoas to keep you in shape? Psoas to keep me limpid. Or just plain old psoas. Didn't even know there was such a thing. Yeah, well, that's the beautiful thing about aging. You find parts of your body you never knew existed only because they hurt. I know. You would think at 35 that you wouldn't be hurting as bad. You would think. Yeah.